Stabilization of photographic materials



United States Patent 01 lice 3,549,371 Patented Dec. 22, 1970 3,549,371 STABILIZATION F PHOTOGRAPHIC MATERIALS Fritz W. H. Mueller, Fritz Dersch, and Giacomo Luciani, Binghamton, N.Y., assignors to GAF Corporation, New York, N.Y., a corporation of Delaware N0 Drawing. Filed Feb. 15, 1968, Ser. No. 705,622 Int. Cl. G03c /30, 5/38 US. Cl. 9666.4 4 Claims ABSTRACT OF THE DISCLOSURE Stabilizers for light-sensitive photographic materials comprising compounds of the following structural formula:

3 f: RC=N-NR1 wherein R and R represent an aromatic nucleus, and R and R are independently selected from the group consisting of hydrogen, alkyl and aryl.

The present invention relates in general to the provision of novel additives for improving the anti-fogging properties, sensitivity, contrast, covering power, etc. of photographic silver halide emulsions and in particular to the employment of hydrazone compounds for such purposes.

As is well known, the sensitivity of light-sensitive silver halide emulsions can be increased in a number of ways as, for example, by the incorporation therein of one or more chemical or optical sensitizing agents which function to augment and/or extend the emulsion sensitivity to light of longer wave lengths.

In general, it is postulated that chemical sensitization results from the formation of small amounts of silver sulfide and/ or silver on the surface of the silver halide crystal. As examples of compounds found to function as chemical sensitizing agents there may be mentioned sodium thiosulfate, sodium sulfite, and the like. Procedures designed to effect chemical sensitization of photographic silver halide emulsions may be implemented for example by carrying out the digestion step in the presence of naturally active gelatin, i.e., active photographically, or alternatively, in the presence of auxiliary sulfur compounds such as those described in US. Pats. 1,574,944, 1,623,499, and 2,410,689. Other procedures of a similar nature involve for example the treatment of the emulsion medium with salts of the noble metals such as ruthenium, rhodium, palladium, iridium and platinum. Representative compounds of this type include, for example, ammoniumchloropalladate, potassium chloroplatinate and sodium chloropalladite, the use of such compounds for sensitizing purposes being described in US. Pats. 2,448,060, 2,566,245, and 2,566,263.

The emulsion may also be chemically sensitized with gold salts such as those described in US. Pat. 2,399,083 or stabilized with gold salts such as those described in US. Pats. 2,597,856 and 2,597,915. Suitable compounds of this type include, for example, potassium chloroaurite, potassium aurothiocyanate, ammonium aurothiosulfate, potassium chloroaurate, and auric trichloride.

Chemical sensitization may also be effected with the use of reducing agents such as stannous salts (US. 2,487,850); polyamines such as diethylene triamine (US. 2,518,698); spermine (U.S. 2,521,925); bis-(fi-aminoethyl) sulfide and its water-soluble salts (US. 2,521,926); formamidine sulfinic acid or derivatives thereof (US. 2,983,609 and US. 2,983,610); imino-amino-methane sulfinic acid (Belgian 547,323); hydrazine and hydroxylamine (French 1,146,955); formaldehyde sulfoxalate (US. 2,604,297); sodium hydrosulfite (US. 1,623,499); organic phosphites (German appl. 1,187,925); ascorbic acid (D5.

2,448,060); etc. Particularly beneficial results as regards efficiency of chemical sensitization are purportedly obtained with such compounds as the polyoxyalkylene ethers and numerous derivatives thereof such as the products obtained by reacting alkylene oxide with reactive hydrogen-containing organic compounds, e.g., acids, alcohols, amines, etc. The use of the foregoing and related compounds for such purposes is well established in the prior art, being extensively described in the patent and trade literature. Other compounds proposed for use in a similar relationship include the quaternary ammonium, phosphonium and ternary sulfonium salts as well as combinations or mixtures of one or more of the foregoing compounds with alkylene oxide polymers.

Other problems frequently encountered in the emulsionmaking as well as the emulsion-processing industries relate to the production of relatively high speed emulsions which enable the attainment of image reproductions characterized by satisfactory contrast as well as covering power of the developed silver. As is well known, the term covering power is a measure of the silver concentration in the developed image and is derived arithmetically by dividing the optical density at maximum density by the grams of silver per square decimeter in the developed image layer.

Representative of the materials heretofore promulgated for use as emulsion addenda to thereby obtain the requisite contrast, silver covering power, etc. include, for example, the poly-N-vinyl lactams, the water-soluble polyglucose dextrans, water-soluble B-hydroxy-alkyl ethers of polyvinyl alcohol, water-soluble hydrolyzed glycogen, water-soluble mannan polysaccharide, the water-soluble polyglucose laminaria, hydroxy-ethyl cellulose, carboxy-methylated proteins, and the like.

While the foregoing and related compounds have been found in the vast majority of instances to provide some measure of improvement, their use is invariably accompanied by other significant drawbacks which tend to detract considerably from their commercial desirability. For example, many of the foregoing compounds must of necessity be employed in inordinately large proportions resulting in a depression of the melting point of the emulsion layer which, in turn, leads to such undesirable defects as reticulation, the latter becoming particularly manifest in those instances wherein the emulsion is subjected to hightemperature, high-speed processing. Moreover, such compound can present serious problems of fog and especially when the emulsion containing same is stored for any significant period of time under even moderately severe conditions of temperature and/or humidity. A further deterrent to the use of the compounds thus far known resides in their pronounced tendency to cause turbidity either in the wet or dry state of the emulsion layer.

In an effort to overcome or otherwise alleviate the foregoing and related disadvantages, considerable industrial research and development has centered around the provision of compounds which, when incorporated into lightsensitive silver halide emulsion layer, impart thereto acceptable photographic speed, contrast and covering power while reducing substantially any tendency of the emulsion to fog. However, despite the extensive industrial effort in this regard, the compounds thus far suggested have been found, characteristically, to provide a satisfactory measure of improvement only at the expense of other essential emulsion properties.

Thus, a primary object of the present invention resides in the provision of improved light-sensitive silver halide emulsions as well as photographic elements fabricated therewith wherein the above and related disadvantages are eliminated or at least mitigated to a substantial extent.

A further object of the present invention resides the provision of improved light-sensitive silver halide emulsions characterized by outstanding improvement in photographic speed, contrast and covering power of the, silver image developed therein.

A still further object of the present invention resides in the provision of improved light-sensitive silver halide emulsion substantially devoid of any tendency to fog and further characterized by outstanding stability even under severe conditions of temperature and/ or humidity.

Other objects and advantages of the present invention will become apparent hereinafter as the description thereof proceeds.

The attainment of the foregoing and related objects is made possible in accordance with the present invention which, in its broader aspects, provides bringing into operative association with a light-sensitive photographic emulsion a hydrazone compound of the following general structure:

wherein R and R represent an aromatic nucleus, e.g.,

benzene or naphthalene; and R and R represent hydrogen, alkyl and preferably lower alkyl of 1 to 4 carbon atoms, e.g., methyl, ethyl, propyl, etc., and aryl, e.g., phenyl. It will be further understood that the aromatic nuclei present in the above-depicted compounds, e.g., at i R and R may further contain substituents of an inert or innocuous nature, the sole limitation with regard to the nature of any such substituents being that they be devoid of any tendency to deleteriously affect the properties desired in the coating composition, such as depressing emulsion, sensitivity, etc. Such substituents may be present for purposes of promoting compatibility with the coating composition, e.g., water-solubilizing groups. As examples of such substituents and found to promote or otherwise augment the efiicacy of the hydrazone compound there may be mentioned, for example, alkyl, alkoxy, nitro, halogen, e.g., chloro, bromo, etc., SO NH CN, groups of the formulae OM, SM, COOM, and $0 M, $0 M, etc. wherein M represents hydrogen, alkyl, aryl, a water-solubilizing cation such as sodium, potassium and ammonium. Thus, the hydrazone compounds contemplated for use in the practice of the present invention may, in addition, be represented according to the following structural formula:

( I ia 1 12 Iii.C-N=N-Rt la wherein R, R R and R have the aforedefined significance and X and X represent nuclear substituents of the type S OaNa S O Na (EH; CH

COOH

COOH

O E O l SH COONa CzHs CH SOzNHz The compounds of the present invention may be prepared according to the method described in Beilstein, vol. XV, p. 134.

In accordance with the discovery forming the basis of the present invention, it has been ascertained that silver halide emulsions of reduced fog, increased speed, contrast, and covering power of the developed silver can be obtained by including the hydrazone compound in the light-sensitive silver halide layer, an undercoating, an intermediate coating, an overcoating and/or a surface coating. The actual coating composition will ordinarily comprise an equeous gelatin solution, and particularly in those instances wherein the composition is intended to be light-sensitive. However, it will be understood that materials other than gelatin may be employed for such purposes, including, for example, a relatively wide variety of organic, polymeric, film-forming materials. Such materials, or film-forming colloids as they are more commonly referred to, may be defined as encompassing those film-forming substances whose aqueout solutions, suspensions, dispersions, emulsions, etc. yield continuous films upon drying. The concentrations employed are not particularly critical so long as sufficient amounts be present to impart to the emulsion the desired characteristics. Thus, the hydrazone compound may be advantageously employed in concentrations varying over a relatively wide range and preferably from about 1 to about milligrams per mole of silver halide.

Within the aforesaid range, the amount selected will depend upon a variety of factors including, for example, the type of emulsion used. With emulsions of the highspeed ammonia type, it is found that the use of 1 to 20 milligrams of the hydrazone compound per mole of silver halide is particularly beneficial. Furthermore, in those embodiments wherein the hydrazone compound is incorporated into a non-sensitized auxiliary layer, e.g., anti-abrasion layer, undercoating, etc., it is usually preferred that such material be utilized in the higher concentration range. In this manner, it is assured that a sufiicient amount of the stabilizer compound will be brought into operative association with the sensitized emulsion layer to thereby realize the improvements contemplated herein. Without intending to be bound by any theory, it has been postulated that the hydrazone compound dilfuses or otherwise migrates to the sensitized emulsion layer thus bringing about the desired intimacy of contact.

When added to the emulsion layer, the addition may be made during the actual preparation of the emulsion, either before or after the emulsion washing step and shortly before coating.

Perhaps the salient advantage presented by the use of the aforedescribed hydrazone compound relates to the fact that the speed of the photographic emulsion is in no way deleteriously affected notwithstanding the use of such compound in relatively large amounts. In fact, quite the contrary would appear to be the case, i.e., the hydrazone additives exhibit a pronounced tendency to beneficially affect the speed characteristics of the film material provided with same. Such compounds are of exceptional value as anti-fogging agents, and since little in the way of limitation is imposed as regards the concentrations employed, significant increases in the photographic speed and contrast of the emulsion as well as the covering power of the developed image are readily obtained despite the use of proportions which would ordinarily, i.e., with the compounds heretofore provided in the art, result in severe fogging. In addition, it is found that the desired emulsion characteristics are obtained even under conditions of high-temperature processing such as those required with the use of modern processing machines. The rather limited properties characterizing the stablizer compounds thus far provided in the photographic art have imposed severe limitations upon the adaptability of photographic elements containing same to high-speed machine processing.

Accordingly, it is of paramout commercial significance that photographic elements prepared with the hydrazone compounds of the present invention are eminently suitable for such high-speed machine processing in the virtual absence of fog, loss of speed, etc.

The following examples are given for purposes of illustration only and are not to be considered as necessarily constituting a limitation on the present invention.

EXAMPLE I A high-speed, sulfur and gold sensitized silver halide emulsion in gelatin containing 4% silver iodide and 96% silver bromide was prepared in a conventional manner and brought up to its maximum light-sensitivity. 'It was then readied for coating on film base, that is, melted at 40 C., necessary coating finals were added such as sensitizing dyes, stabilizers and hardeners, A 0.1% solution of N- methyl-p-sulfophenylhydrazone, o-sulfobenzaldehyde disodium salt in water was prepared and a portion of this solution added to a sample of the above-described emulsion containing about 0.6 mole of silver halide. A sample of the same emulsion, but not containing the compound of the present invention, served as a control. The thus- Quantity of compound used per 0.6 mole of silver Relative Fog, halide tg.) speed 6 dev.

EXAMPLE II Example I is repeated, except that the solvent employed comprises dimethyl formamide instead of Water and the results obtained are as follows:

Quantity of compound used per 0.6 mole of silver Relative Fog,

halide (g.) speed 6 dev.

EXAMPLE HI A high-speed, sulfur and gold sensitized silver halide emulsion in gelatin containing 2% silver iodide and 98% silver bromide was prepared in a conventional manner and brought up to its maximum light-sensitivity. It was then readied for coating as described in Example I. Also, samples were prepared as in Example 1. Test and control were then developed in the Eastman Kodak M4 X-Omat processing system. The results obtained were as follows:

Quantity of compound Relative used (g.) speed Fog EXAMPLE IV A high-speed, sulfur and gold sensitized silver halide emulsion containing 2% silver iodide and 98% silver bromide was prepared. Samples containing about 0.4 mole of silver halide were treated as follows:

(a) Coated as control and provided with a 4n surface coating prepared from 20 grams gelatin in 1 liter water.

(b) As (a) but to the'l liter of surface solution was added 15 grams of propylene oxide treated gelatin (see co-pending patent application Ser. No. 319,969, filed Oct. 30, 1963).

(c) Like (b) but to the emulsion sample were added 0.02 gram N-methyl-p-sulfophenylhydrazone, o-sulfobenzaldehyde disodium salt dissolved in dimethyl formamide.

The testing material (a), (b) and (c) was sensitometrically exposed and developed in the M4 X-Omat system with the following results being obtained:

Despite the improved covering power, the melting point of the emulsion was not reduced and a scratch test showed no increased scratch tendency.

EXAMPLE V A silver halide emulsion in gelatin containing 2% silver iodide and 98% silver bromide was coated on film base in a manner known to the art. After the coating, a solution containing 20 grams of gelatin in 1 liter of H 0 and a 0.1% solution of N-methyl-p-sulfophenylhydrazone,

o-sulfobenzaldehyde disodium salt in water was coated thereon as an anti-abrasion layer. After drying, film samples Were exposed and processed as described in Example I.

Quality of com- Relative pound Fog, speed used(g.) 3 dev. 3 dev.

EXAMPLE VI A high-speed, sulfur and gold sensitized halide emulsion containing 2% silver iodide and 98% silver bromide was prepared. Samples containing about 0.4 mole of silver halide were treated as follows:

(a) Coated as control and provided with a 4,11. surface coating prepared from grams gelatin in 1 liter water;

(b) As (a) but to 1 liter emulsion was added 0.3 gram of polyoxyalkylene ether, Brij 35.

(c) Like (b) but to the emulsion sample were also added 0.02 gram N-methyl-p-sulfophenylhydrazone, osulfobenzaldehyde disodium salt.

The testing material (a), (b) and (c) was sensitometrically exposed and developed in the M4 X-Omat system, with the following results being obtained:

Speed Fog Experiment;

The present'invention has been disclosed with respect to certain preferred embodiments and there will become obvious to persons skilled in the art various modifications, equivalents or variations thereof which are intended to be included within the spirit and scope of the present invention.

What is claimed is:

1. A light-sensitive photographic material comprising a base and at least one light-sensitive silver halide emulsion, said photographic material containing a stabilizer of the following structural formula:

R3 R2 R=N-I TR1 wherein R and R represent an aromatic nucleus, and R and R are independently selected from the group consisting of hydrogen, alkyl and aryl.

2. A light-sensitive photographic material according to claim 1 wherein said stabilizer compound is present in a 1surface coating overcoating said silver halide emulsion ayer.

3. A light-sensitive photographic material according to claim 2 wherein said stabilizer comprises N-methyl-psulfophenylhydrazone, o-sulfobenzaldehyde disodium salt.

4. A process for treating an exposed silver halide emulsion material which comprises developing said material in the presence of a stabilizer compound comprising a compound of the following structural formula:

If; R: RC=N-}|TR1 wherein R and R represent an aromatic nucleus, and R and R are independently selected from the group consisting of hydrogen, alkyl and aryl.

References Cited UNITED STATES PATENTS 2,353,690 7/1944 Clarkson 4464 NORMAN G. TORCHIN, Primary Examiner E. C. KIMLIN, Assistant Examiner US. Cl. X.R. 96-66.4, 109 

